blob: 2a1b0d762450204243b05b4d17cde3158613edfb
| 1 | /* |
| 2 | * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at> |
| 3 | * |
| 4 | * This file is part of FFmpeg. |
| 5 | * |
| 6 | * FFmpeg is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU Lesser General Public |
| 8 | * License as published by the Free Software Foundation; either |
| 9 | * version 2.1 of the License, or (at your option) any later version. |
| 10 | * |
| 11 | * FFmpeg is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | * Lesser General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU Lesser General Public |
| 17 | * License along with FFmpeg; if not, write to the Free Software |
| 18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 19 | */ |
| 20 | |
| 21 | /** |
| 22 | * @file |
| 23 | * @ingroup lavu_crc32 |
| 24 | * Public header for CRC hash function implementation. |
| 25 | */ |
| 26 | |
| 27 | #ifndef AVUTIL_CRC_H |
| 28 | #define AVUTIL_CRC_H |
| 29 | |
| 30 | #include <stdint.h> |
| 31 | #include <stddef.h> |
| 32 | #include "attributes.h" |
| 33 | #include "version.h" |
| 34 | |
| 35 | /** |
| 36 | * @defgroup lavu_crc32 CRC |
| 37 | * @ingroup lavu_hash |
| 38 | * CRC (Cyclic Redundancy Check) hash function implementation. |
| 39 | * |
| 40 | * This module supports numerous CRC polynomials, in addition to the most |
| 41 | * widely used CRC-32-IEEE. See @ref AVCRCId for a list of available |
| 42 | * polynomials. |
| 43 | * |
| 44 | * @{ |
| 45 | */ |
| 46 | |
| 47 | typedef uint32_t AVCRC; |
| 48 | |
| 49 | typedef enum { |
| 50 | AV_CRC_8_ATM, |
| 51 | AV_CRC_16_ANSI, |
| 52 | AV_CRC_16_CCITT, |
| 53 | AV_CRC_32_IEEE, |
| 54 | AV_CRC_32_IEEE_LE, /*< reversed bitorder version of AV_CRC_32_IEEE */ |
| 55 | AV_CRC_16_ANSI_LE, /*< reversed bitorder version of AV_CRC_16_ANSI */ |
| 56 | #if FF_API_CRC_BIG_TABLE |
| 57 | AV_CRC_24_IEEE = 12, |
| 58 | #else |
| 59 | AV_CRC_24_IEEE, |
| 60 | #endif /* FF_API_CRC_BIG_TABLE */ |
| 61 | AV_CRC_MAX, /*< Not part of public API! Do not use outside libavutil. */ |
| 62 | }AVCRCId; |
| 63 | |
| 64 | /** |
| 65 | * Initialize a CRC table. |
| 66 | * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 |
| 67 | * @param le If 1, the lowest bit represents the coefficient for the highest |
| 68 | * exponent of the corresponding polynomial (both for poly and |
| 69 | * actual CRC). |
| 70 | * If 0, you must swap the CRC parameter and the result of av_crc |
| 71 | * if you need the standard representation (can be simplified in |
| 72 | * most cases to e.g. bswap16): |
| 73 | * av_bswap32(crc << (32-bits)) |
| 74 | * @param bits number of bits for the CRC |
| 75 | * @param poly generator polynomial without the x**bits coefficient, in the |
| 76 | * representation as specified by le |
| 77 | * @param ctx_size size of ctx in bytes |
| 78 | * @return <0 on failure |
| 79 | */ |
| 80 | int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size); |
| 81 | |
| 82 | /** |
| 83 | * Get an initialized standard CRC table. |
| 84 | * @param crc_id ID of a standard CRC |
| 85 | * @return a pointer to the CRC table or NULL on failure |
| 86 | */ |
| 87 | const AVCRC *av_crc_get_table(AVCRCId crc_id); |
| 88 | |
| 89 | /** |
| 90 | * Calculate the CRC of a block. |
| 91 | * @param crc CRC of previous blocks if any or initial value for CRC |
| 92 | * @return CRC updated with the data from the given block |
| 93 | * |
| 94 | * @see av_crc_init() "le" parameter |
| 95 | */ |
| 96 | uint32_t av_crc(const AVCRC *ctx, uint32_t crc, |
| 97 | const uint8_t *buffer, size_t length) av_pure; |
| 98 | |
| 99 | /** |
| 100 | * @} |
| 101 | */ |
| 102 | |
| 103 | #endif /* AVUTIL_CRC_H */ |
| 104 |